Organomagnesium complexes having enhanced storage stability



United States Patent 3 187 663i ORGANOMAGNESIiJM CGWLEXES HAVENGENHANCED STORAGE dTAEHdTY Francis H. Bratton, Northfield, Mind, andFrancis J.

Buescher, Alfred H. Frye, and Victor G. Sonkup, Cincinnati, ()hio,assignors to The Cincinnati Milling Machine (10., Cincinnati, Ghio, acorporation of Ohio N0 Drawing. Filed June 13, 1962, Ser. No. 292,952

17 Claims. (Cl. 26665) This invention relates to stabilizedorganomagnesium complexes and to a process for their preparation.

As used herein, the term organomagnesium complex refers to magnesiumcontaining organic compounds in which the magnesium atom is bounddirectly to at least one carbon atom by a bond which is predominantlycovalent in character. Examples of such organomagnesium complexes arethe classical Grignard reagents or the magnesium dialkyls or diaryls,the latter two being illustrated by dibutyl magnesium and diphenylmagnesium.

It is known that organomagnesium complexes leave much to be desired fromthe standpoint of storage stability. To measure deterioration orinstability a test was devised which is herein referred to as astability test. In accordance with this test the organomagnesium complexin a normally liquid medium is placed in containers which are closed tothe atmosphere and kept in the dark at the ambient temperature (about 25C.) for a period of four weeks. The containers are opened to theatmosphere in the light for one five minute interval in the one day testand twice a week for the tests of longer duration. One container ofmaterial is used for each analysis. The analyses are carried out atleast 24 hours after exposure.

Initial values were established from unexposed samples which wereanalyzed for activity. The containers used in this test are wide-mouth,screw-cap, clear glass bottles of either 12 ounce (354 ml.) or 16 ounce(473 ml.) size. Each test is performed in such a way that the air spacein the capped bottle is 100:5 ml. In other words, the total volume ofthe condensed phases (i.e., solids plus liquids) amounts to 255 :5 ml.in the 12 ounce bottles or 370:5 ml. in the 16 ounce bottles. Adjustmentof the volume of the condensed phases to the desired volume is achievedin the following three ways: (1) Glass marbles are added to increase thevolume, (2) Additional hydrocarbon is added to increase the volume, or(3) In cases where the volumes of the condensed phases are too great,the contents of the bottles are allowed to settle and the excesssupernatant liquid is removed by pipette and assayed for organomagnesiumcontent. During the periods when the test bottles are uncapped andexposed to the atmosphere, they are removed from the dark room orcabinet where they are normally stored and the exposure takes lace undernormal laboratory illumination (daylight plus fluorescent ceilinglights). After the exposures are complete the bottles are returned tothe dark room or cabinet. The final analyses are always performed undernormal laboratory illumination.

Organomagnesium complexes (Grignard reagents, dialkyl-magnesiums,diarylmagnesiums, etc.) are known to be decomposed by reaction withvarious normal atmospheric components, viz., water, carbon dioxide andoxygen. The stoichiometry of these reactions may be written as follows:

RMgX+H O RH+Mg(OI-I)X R Mg+2H O- 2RH+Mg(OI-l) RMgX-}-CO R-CO MgX RMgX+O"RO MgX 2 2 2)2 where R represents the organic radical and X is halogen.

Eddifihi By means of the Gilman method of analysis it is not possible todistinguish between active organomagnesium complex and the productsformed by the interaction of the reactive components in the atmospherewith the ac tive organomagnesium complex, the Gilman method beingessentially an analysis for magnesium bases. Thus, in the Gilmananalysis one treats the sample of organemagnesium complex with an excessof dilute hydrochloric acid and then determines the amount of excesshydrochloric acid present by titration with standard sodium hydroxidesolution EH. Gilman, P. D. Wilkinson, W. P. Fischel and C. H. Meyers, J.Am. Chem. Soc., 45, 150 (1923) Since the decomposition of theorganomagnesium complexes under the conditions of the present stabilitystudies is most plausibly rationalized as resulting from their attack byatmospheric components during (and following) the periods of atmosphericexposure, it is obvious that the Gilman method of analysis would not beuseful. A method was employed, therefore, in which the sample to beanalyzed is subjected to carboxylation by treatment with Dry Ice (solidcarbon dioxide) in an ethereal medium and the amount of carboxylic acidformed then determined by acid-base titration, the pertinent equationsbeing:

(It is, of course, obvious that analysis by this carboxylation techniquecannot distinguish between the organomagnesium complex which has reactedwith atmospheric carbon dioxide and that which has reacted with the Dry-Ice, however the small amount of carbon dioxide normally present in theatmosphere warrants neglect of this factor.)

According to this procedure, the cap of the bottle, in which the samplewas stored, is removed and in its place is inserted a rubber stopperthrough which run two pieces of /4 inch glass tubing.

The tubing extends but slightly beyond the lower surface of the stopperand serves initially to displace the air in the bottle with nitrogen.After permitting a gentle stream of nitrogen to flow through the bottlefor 5 minutes, the stopper is carefully lifted and approximately -100ml. of sodium-dried ether (or, in certain instances, tetrahydrofuran)are introduced into the bottle and the stopper reinserted. The bottle isthen swirled to cause dissolution of the organomagnesium complex.Meanwhile, in a 4-liter beaker there is placed approximately 1 liter ofcrushed Dry Ice, together with sufficient sodium dried ether (ortetrahydrofuran in some cases) to furnish a slurry. The outlet tube inthe rubber stopper is then pushed to the bottom of the storage bottleand the ethereal solution of the organomagnesium complex caused to flowthrough that tube and into the beaker containing the ether and the DryIce, the Dry Ice-ether mixture being thoroughly stirred during theaddition. In order to insure the quantitative transferrai of all theorganomagnesium complex to the beaker, two additional portions (ca. 300ml. each) of sodium dried ether (or tetrahydroturan) are carefully addedin sequence to the bottle and the solution then expressed into thebeaker. Finally, a fourth portion of ether (or tetrahydrofuran) is addedto the bottle together with some Dry Ice, the mixture stirred and pouredinto the 4-liter beaker. The contents are then thoroughly stirred andallowed to stand uncovered overnight in the fume hood, during which timethe bulk of the ether evaporates.

The next day, the residue in the beaker (a dry, grey cake) is stirredwith 6-8 cubes of ice until the mixture is reasonably well dispersed,whereupon an excess of approximately l-N hydrochloric acid is added andthe mixture transferred to a SOS-ml. separatory funnel. The

aqueous layer is withdrawn and the organic material remaining in theflask washed with several small portions of water, the washings beingcombined with the aqueous layer. The aqueous layer is then extractedwith two 50- ml. portions of heptane and the heptane extracts combinedwith the organic layer, the combined material transferred to a ZSO-ml.volumetric flask, and the contents made up to the mark by the additionof ether. After shaking the mixture thoroughly, a 25-ml. aliquot isWithdrawn and titrated with 0.l-N sodium hydroxide solution to determinethe amount of carboxylic acid present therein. From this information,together with information bearing on the amount of carboxylic acid whichcan be obtained from a standard freshly prepared organomagnesiumcomplex, one can calculate the amount of organomagnesium complex whichhas deteriorated under the test conditions.

One milliequivalent of active organomagnesium complex furnishes intheory one milliequivalent of carboxylic acid in the above procedure.

' When solutions of various Grignard reagents in ether type solventswere subjected to the foregoing stability test, it was noted that thereduction in activity was practically a straight line function of thetime and at the end of the four'week period more than half of theinitial activity had been lost.

One of the objects of the invention is to provide compositionscontaining organomagnesium complexes which are sufiiciently stabilizedto permit containers containing these compositions to be stored andsubjected to intermittent atmospheric exposure over a period of at leastfour weeks while still retaining a major proportion, and

preferably at least 70%, of the initial activity.

7 A further object of the invention isto provide a method andcompositions for enhancing the storage stability of organomagnesiumcomplexes so that they can be sold as such and used as desired incarrying out chemical reactions by withdrawing them from storage atintervals without taking any unusual precaution during the storageperiod.

Another object of the invention is to provide organomagnesium complexesof enhanced stability in which the hazard associated with such complexesis vastly less than that with the highly flammable and even explosiveethers of the conventionally prepared organomagnesium complexes.

A more specific object of the invention is to provide a new and improvedmethod for stabilizing organomagnesium complexes which retards loss ofthe'activity of the organomagnesium complexes on storage.

'Another specific object is the provision of new an improved stabilizedcompositions containing organomagnesium complexes. Other objects willappear hereinafter.

In accomplishing these objects in accordance with the invention it hasbeen found that enhanced storage stability is obtained by preparingcompositions which consist essentially of ether-free organomagnesiumcomplexes in hydrocarbon media, which media may be either individualinert hydrocarbon compounds or mixtures of such compounds, but whichmedia are liquid at room temperature (about 25 C.), and which, whenslurried with an excess of the organomagnesium complexes at 25 C. andthe slurries then allowed to settle until their supernatant liquid phaseseparates, have supernatant liquid phases in which the concentrations ofthe organomagnesium complexes do not exceed 35 milliequivalents (meq.)per 100 ml. of the liquid phase, and preferably do not exceed 10milliequivalents of organomagnesium complex per 100 ml. of the liquidphase.

The invention will be further illustrated but is not limited by thefollowing examples in which the quantities are stated in parts by weightunless otherwise indicated.

:In these examples various ether-free organomagnesium complexes wereprepared in liquid hydrocarbon media. Samples of the compositions wereplaced in closed containers under substantially identical conditions andstability tests were carried outwith exposure to the atmosphere asfollows:

Storage time:

1 day conditions Sample given a 5-minute exposure to the atmosphere andanalyzed after a least 24 hours a Sample given two S-minuteexposuresspaced at equal intervals during the week 1 week 2 weeks spaced at equal2 weeks a Sample given'eight 5-minute exposures spaced at equalintervals during the 4 weeks 7 Hence a four week stabilitytestrepresents a minimum of eight container openings and a total time ofexposure of the organomagne'sium complex to the atmosphere of 40minutes. ,The discontinuous exposure, namely, that of eight exposures offive minutes each, provides eight separate new atmospheres to thecomplex, each being present for a prolonged reaction period.

In effect this is the same as if a user were to make eight separatewithdrawals of material from the container over a four week period. Thetest is intended to simulate the typical conditions that might beencountered in commercial usage. 7

The following results were obtainedz intervals during the 4 weeksConcentration of organomagnesium complex in supernatant hydrocarbonmedium Sample given four 5-minute exposures 115.6 meqJlOO ml.

Organomagnesimn complex prepared irom phenyl chloride and magnesium inStoddard solvent:

1 day97.5% remaining 1 week97.4% remaining 2 weeks-95.5% remaining 4weeks88% remaining III 1.9 meq./100 ml.

IV- Organomagneslum complex prepared trom butyl chloride and magnesiumin cyclohexane:

1 day-95.3% remaining 1 week-90.6% remaining.-- 2 weeks73.6% remaining 4weeks-69.7% remaining Organoma-gnesium complex prepared from butylchloride and magnesium in a 1: 1 ratio (volunre) cyclohexane-heptanez 1day-99.5% remaining 1 week-94.7% remaining..- 2 weeks-85.5% remaining 4weeks-85.4% remaining Organomag'nesium complex pre- 16.2 meq./100 ml.

- pared from butyl chloride and magnesium in 2,2,4-trimethylpentane: V

1 dayl00% remaining 1 week-94.4% remaining"- 2 weeks85.8% remaining" 4weeks-86.2% remaining-.-

0.01 meqJlUO ml.

Organomagnesium complex prepared from phenyl chloride and magnesium incyclooctane:

1 day-100% remaining 1 week-92% remaining 2 weeks-456.0% remaining 4weeks-% remalning VIL 9.7 meq./ ml.

7 is between a minimum of and a maximum of 70% by weight of saidorganornagnesium complex.

7. A composition of enhanced storage stability consisting essentially ofa mixture of an ether-free organomagnesium complex formed from theinteraction of an organic halide with magnesium and a quantity of ahydrocarbon medium liquid at C. sufiicient to permit the presence of asupernatant liquid phase when the mixture is allowed to settle, thehydrocarbon medium being one which when slurried with saidorganomagnesium complex at 25 C. and allowed to settle gives asupernatant liquid phase in which the concentration of theorganomagnes'ium complex does not exceed milliequivalents per 100milliliters of the liquid phase.

'8. A composition of enhanced storage stability comprising a mixture ofa minimum of at least 5% by weight and -a maximum of not more than 70%by weight of an ether-free organomagnesium complex formed from theinteraction of an organic halide with magnesium and a quantity of astabilizing medium which is liquid at 25 C. sufficient to permit thepresence of a supernatant liquid phase when the mixture is allowed tosettle, said stabilizing medium consisting essentially of at least onehydrocarbon which is liquid at 25 C., said hydrocarbon when slur-riedwith said organom'agnesium complex at 25 C. and allowed to settle givinga supernatant liquid phase in which the concentration of saidorganomagnesium complex does not exceed 35 milliequivalents per 100milliliters of the liquid phase, the amount of said hydrocarbon liquidbeing sufiicient to enhance the storage stability of saidorganomagnesium complex.

9. A composition as claimed in claim 8 in which the alkyl chloride andmagnesium.

10. A composition as claimed in claim 8 in which the organomagnesiumcomplex is formed from an aryl chlowith said organomagnesium complex andthe slurry allowed to settle gives a supernatant liquid phase in whichthe concentration of the organomagnesium complex is not in excess of 35milliequivalents per 100 milliliters of said liquid phase, the quantityof said hydrocarbon being 'organom-agnesium complex is formed from aprimary sufficient to enhance the storage'stability of said organomagnesium complex.

12. A process of enhancing the storage stability of an ether-freeorganomagnesium complex which comprises forming a mixture of suchcomplex with a quantity of a liquid hydrocarbon medium sufiicienttopermit the presence of a supernatant liquid phase when the mixtureisallowed to settle, the hydrocarbon medium being one which is liquid at25 C. and which when slurried at 25 C. with said organornagnesiumcomplex and the slurry al lowed to settle gives a supernatant liquidphase in which the concentration of the organomagnesium complex is notin excess of 10 milliequivalents per 100 milliliters of said liquidphase, the quantity of said hydrocarbon being suiiicient to enhance thestorage stability of said organomagnesium complex.

13. A process as claimedin claim 11 in which a mixture of hydrocarbonsliquid at 25 C. is used.

14. A process as claimed in claim 11 in which the hydrocarbons liquid'at25 C. are from the group consisting of aliphatic and alicyclichydrocarbons and mix-- organomagnesium complex is a Grignard reagentderived.

from an aryl chloride and magnesium.

References Cited by the Examiner UNITED STATES PATENTS 3,095,460 6/63Olah 260665 OTHER REFERENCES Kharasch et al.: Grignard Reactions ofNonmetallic Substances, Prentice-Hall Inc., New York, 1954, pages -53.

Coates: Organo-Metallic Compounds, 2nd ed., Wiley & Sons, Inc., NewYork, 1960, page 54.

Rochow et .al.: The Chemistry of Organometal-lic Com: pounds, Wiley &Sons, New York, 1957, pages 82, 84, and 88.

TOBIAS E. LEVOW, Primary Examiner.

. ALPHONSO D. SULLIVAN, Examiner.

1. A COMPOSITION OF ENHANCED STORAGE STABILITY CONSISTING ESSENTIALLY OFA MIXTURE OF AN ETHER-FREE ORGANOMAGNESIUM COMPLEX IN A QUANTITY OF ALIQUID HYDROCARBON MEDIUM SUFFICIENT TO PERMIT THE PRESENCE OF ASUPERNATANT LIQUID PHASE WHEN THE MIXTURE IS ALLOWED TO SETTLE, THEHYDROCARBON MEDIUM BEING ONE WHICH IS NORMALLY LIQUID AT ROOMTEMPERATURE AND WHICH WHEN SLURRIED WITH THE ORGANOMAGNESIUM COMPLEX AT25*C. AND THE SLURRY THEN ALLOWED TO SETTLE GIVES A SUPERNATANT LIQUIDPHASE IN WHICH THE CONCENTRATION OF THE ORGANOMAGNESIUM COMPLEX DOES NOTEXCEED 35 MILLIEQUIVALENTS PER 100 MILLILITERS OF THE LIQUID PHASE.